1. Field of the Invention
The present invention relates to a gene sequence of superoxide dismutase of Aquifex pyrophilus and protein expressed in Escherichia coli.
2. Description of the Prior Art
Recently, there has been a variety of attempts to isolate enzymes from the organisms which may grow in a specific environment, or to modify a known enzyme so as to obtain an enzyme which can maintain its activity in a specific environment. In particular, the presence of an organism which can grow in temperatures around 100.degree. C. or higher has been reported, and it has been known that an enzyme isolated from such a organism can also maintain its activity at a high temperature of around 100.degree. C. without being denatured. Therefore, there have been extensive attempts to find a hyperthermophilic enzyme which is active at a high temperature from such microorganisms. Microorganisms which may grow at an extremely high temperature are collectively referred to as "hyperthermophile" and their optimum growth temperature is normally a temperature of at least 80.degree. C. It has also been reported that some kinds of microorganisms may grow even at an extremely higher temperature of at least 115.degree. C. Now, it has been reported that there are about at least 50 to 60 kinds of hyperthermophile, and they are largely distributed at deep thermal vent regions. Most hyperthermophile are classified as a kind of archaeobacteria or archaea, among which are two species of Thennotoga and Aquifex which belong to a class of bacteria.
The results of 16s RNA sequence analysis indicated that A. pyrophilus of Eubacterium is located at the lowest part of the evolution map. They are known as an autotrophic bacterium which can oxidize or reduce sulfur atom to produce energy. [See, Huber R. et al., Syst. Appl. Microbiol. 15: 349-351, 1992]. A. pyrophilus was discovered in deep submarine. It also has been found that the organism may grow between 67.degree. C. and 95.degree. C. and its optimum growth temperature is 85.degree. C.
Superoxide dismutase (hereinafter. referred to SOD) is an enzyme which can convert superoxide radicals (O.sub.2 --) to H.sub.2 O.sub.2. The superoxide radicals are chemically and inevitably generated in vivo. The enzyme is one of the important enzymes to function in the intracellular protection mechanisms. [See, Fridovich, I. et al., Annu. Rev. Biochem. 64, 97-112]. SODs are divided into three species, i.e., Cu- and Zn-, Fe-, and Mn-SOD in accord with the kind of bound metal. Cu-, and Zn-SOD are found in eucaryote, Fe-SOD in eubacteria and archaeobacteria, and Mn-SOD in bacteria and mitochondria of eucaryote.
As disclosed above, the superoxide dismutase involves an important protection mechanism to prevent cellular lesions due to oxygen. Therefore, the enzyme may be useful for the preparation of necessary medicaments for treating inflammation, disease of autoimmunization, chromosomal lesion and the like. Particularly, A. pyrophilus is one of hyperthermophilic bacteria which can grow at the optimum temperature of 85.degree. C., so that the superoxide dismutase of A. pyrophilus has a higher thermal stability than other organisms and is further broadly applicable in the field of the pharmaceutical industry.